Walk behind lawn mowers are well known outdoor power equipment units for mowing grass. Such mowers comprise a movable housing having a cutting chamber that carries a substantially horizontal rotary cutting blade. A handle extends upwardly and rearwardly from the housing. An operator grips a handle grip on the handle and walks behind the mower to guide and control the mower.
Many walk behind lawn mowers have a self propel system that propels or drives the mower at a variable ground speed. In such mowers, some type of control system is carried on the handle to allow the operator to engage and disengage the self propel system and to select a desired ground speed. Many such control systems utilize a pivotal ground speed control bail on the handle of the mower. The bail can be pivoted from an open position towards a closed position to engage the self propel system. In some control systems, the degree of closure of the ground speed control bail determines the ground speed of the mower.
U.S. Pat. No. 6,082,083 to Stalpes et al., assigned to The Toro Company, the assignee of this invention, discloses a different control system for operating the self propel system of a mower or the like. The control system of the 083 patent includes a handle grip on the handle that slides up and down relative to a lower portion of the handle. As the handle grip slides down, the mower ground speed increases. As the handle grip slides up, the mower ground speed decreases.
The slidable handle grip of the 083 patent automatically adjusts the ground speed of the mower to the walking speed of the operator. If the operator walks faster, the operator naturally pushes somewhat harder on the handle grip, thereby sliding it further down which increases the mower ground speed. Conversely, if the operator walks slower, the operator naturally pushes with less force on the handle grip, which allows the handle grip to rise thereby decreasing the mower ground speed. This control system has been commercially successful in the Personal Pace line of Toro lawn mowers and the Easy Stride line of Lawn Boy lawn mowers.
In the control system of the 083 patent, the handle grip comprises a transverse cross bar, two downwardly extending legs, and an escutcheon plate all integrally molded as a single piece out of plastic. The legs of the handle grip telescopically slide over the outer diameter of the upper ends of the handle tubes of the handle. Plastic slide bushings are placed between the handle tubes and the handle grip to prevent wear on the legs of the handle grip. A separate control bail is pivotally mounted on the handle grip for controlling the operation of the blade by allowing operation of the engine.
While the above described handle grip is effective, it is somewhat complex and involves numerous components. A simpler structure for the handle grip and for slidably mounting the handle grip on the handle would be desirable for cost reduction.
In addition, when using the control system of the 038 patent, one phenomenon that has been observed is a tendency for the mower to slow down. The operator can compensate for this by pushing in harder on the slidable handle grip. But, this requires the operator to consciously adjust the position of the handle grip. It would be desirable to provide the operator with the ability to temporarily and selectively increase the mower ground speed without having to do so through direct manipulation of the slidable handle grip itself. However, this has not heretofore been possible.
Finally, even when travelling on flat terrain, the slidable handle grip of the 038 patent can result in uneven ground speed for some operators due to an inconstant pushing force on the slidable handle grip. Moreover, once an operator finds a position of the slidable handle grip that produces a mower ground speed that is to the operator's liking, the operator must pay close attention to keeping the handle grip in that same position to keep the ground speed constant. It would be desirable to have some way of establishing and maintaining a constant position of the slidable handle grip to provide a cruise control. Again, this was not possible prior to this invention.